In reference to this thread
The easiest way to find the two errors is doing a search on both plugins for “tribe_events_page_tickets-attendees”.
They are in event-tickets-plus/src/Tribe/Meta/Export.php and event-tickets/src/Tribe/Attendees.php
In both cases $post_type. manage_{$post_type}_columns
is what was in the code, but it should be
manage_{$post_type}_post_columns
I cannot find documentation on a manage_{$post_type}_columns filter. there is a manage_edit-{$post_type}_column filter.
In any case, the fix I have proposed fixes the issue. Obviously I haven’t done any regression testing. attached is a zip containing Export.php for tickets plus. I will send the pull request to https://github.com/moderntribe/event-tickets momentarily.